Research On Global Quark Polarization And Bulk Viscosity Effect Of Quark Matter

The first two chapters are about global quark polarization of quark matter produced in heavy ion collisions.A longitudinal fluid shear of partons that produced in the early stage of non-central heavy ion collisions can be developed due to unequal local number densities of participant target and projectile nucleons.Local patton pairs with non-zero impact parameters have finite local relative orbital angular momentum in the direction opposite to the reaction plane.Such finite relative orbital angular momentum among locally interacting quark pairs can lead to global quark polarization due to spin-orbital coupling.The global polarization was obtained with small angle approximation in an effective potential model.We extended the model to include the effect of the thermal medium and used hard-thermal-loop resummed gluon propagator.We calculated the global polarization with and beyond small angle approximation.Our results show that the polarization is sensitive to the ratio of the incident energy to temperature of the medium.There are ambiguity in the calculation of differential cross section in impact parameter space with the conventional approach.We derived it in quantum field theory and reproduced the same result with conventional one in the leading order of small angle scattering.Polarization of quark-gluon scattering was also calculated in the new approach.All pulsars will develop an r-mode instability if they are treated as ideal fluid. R-mode will lead to the production of gravitational waves and carry off the angular momentum and the rotational energy and make the rotation of pulsars slow down. Bulk viscosity can suppress these instabilities.We obtain an universal expression for the bulk viscosity for multi-component fluid which can reproduce the result of simple fluid.We derived the bulk viscosity in entropy approach and obtain results for multi-component fluid with a variety of reactions and oscillation patterns.The approach guarantees the positivity of the bulk viscosity explicitly.